Telephone-exchange system



April 14, 1925. 1,533,203

P. B. MURPHY TELEPHONE EXCHANGE SYSTEM I Filed April 5, 1921 4 Sheets-Sheet 1 g g it T" Q u is s MM-o l I I Him-Ilv Ari/anion- Pau/ 5. Murphy ase-J April 14, 1925. 1,533,203

I P. B. MURPHY TELEPHONE EXCHANGE SYSTEM Filed April 5, 1921 4 Sheets-Sheet 2 Z w47fy April 14, 1925. 1,533,203

- P. B. MURPHY TELEPHONE EXCHANGE SYSTEM Filed April 5, 1921 4 Sheets-Sheet 5 //7l//77 0/? Pau/ 15. May/7y A ril 14, 1925. 1,533,203

I P. B. MURPHY TELEPHONE EXCHANGE SYSTEM Filed April 5, 1921 4 Sheets-Sheet 4 Pau/ 5f Mum/7y Patented Apr. 14, 1925.

UNITED STATES PATENT OFFICE.

PAUL IB. MURPHY, 0F NYACK, NEW YORK, ASSIGNOR T0 WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N.

Y., A CORPORATION OF NEW YORK.

TEEPHONE-EXCHANGE SYSTEM.

Application filed Apri1'5, 1921. Serial No. 458,712.

To all whom it may concern.-

Be it known that I, PAUL B. MURPHY, a citizen of United States, residing at Nyack, in the county of Rockland, State of New York, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems and more particularly to those in which oilices are interconnected by call wire toll lines.

In systems of this nature it is the usual practice for an operator at the originating office to establish and supervise the connection in the same manner as in the usual common battery trunk connection between local oiiices in the same exchange district.

It is an object of this invention to provide an improved call wire toll .line system which will possess all of the advantages of circuits arranged .for ring-down operation. The latter type of line may be arranged to use the line conductors also for telegraph operation, which is a valuable feature; while a toll line designed for common battery supervision cannot readily be so used.

It is also an object to provide a call Wire toll line system which is readily adapted to use on very long lines which, in order to provide good telephonic transmission, are usually equipped with repeater stations.

. The present system of battery supervisory signaling, used on toll lines, is not conveniently adaptable to repeater lines, not only on account of their high resistance, but also on account of the difliculty of providing therefor a circuit either through or around the repeater station.

Another object is to control a vacuum tube oscillator for producing oscillations of a multiplicity of frequen ies to select groups of frequencies and sequentially impress the frequencies of a selected group upon a circuit.

It is a further object to provide a call wire toll line system which can be readily applied to carrier telephone and telegraph lines, which lines cannot be readily used for battery supervision because of their high resistance. The system of this invention may be readily used in connection with this type of toll line without in any way curtailing its usefulness;

Further objects are to signal a called station and to supervise the connection thereto by the transmission and the selective receiving of predetermined combinations of current impulses of different frequencies.

To attain the above mentioned objects in accordance with a feature of this invention, sources of currents of various frequencies are provided at both the outgoing and incoming ends of the toll line with corresponding receiving circuits also at each end. Means is provided for automatically transmitting from each sending circuit various predetermined combinations of currents which cause the respective receiving circuits to function correspondingly to perform all of the various signaling and switching functions necessary to the establishment and dis establishment of the connection.

The system of signaling'that is used is essentially that of the applicants copending application Serial No. 379,705, filed May 8, 1920, which discloses a system of signaling using currents of a frequency within the voice range. Currents of this frequency are generally the most useful for transmission over telephone lines, since such lines are designed to operate most efficiently when currents of voice frequencies are transmitted thereover. However, currents of any frequency which may be transmitted elliciently through the connecting medium may be used.

The nature of the invention will more fully appear from the following specification and accompanying drawings in which the figures represent diagrammatically the circuits used to connect the two subscribers telephone stations by means of the call wire toll line circuit which is the subject of this invention.

The invention is embodied in Fig. 2 and Fig. 3 of the drawing. Fig. 1 and Fig. 4 show circuit arrangements well known in the art and which are shown only to describe conveniently and completely, the working of the invention.

Figs. 1, 2, 3 and 4 when arranged, in accordance with the arrangement of F g. 5, show the interconnecting circuits used in establishing a connection between any two subscribers stations, 100 and 400, whose lines may terminate at switchboards located in distant cities,- which switchboards may be connected by a call wire trunk line L, the outgoing and incoming ends of which, with associated apparatus, are shown in Fig. and Fig. 3, respectively. Altl 1ough an ordinary two' wire metallic line is indicated as the transmission medium between the two ofiices, it is to be understood that any other suitable medium may be used.

The substation '100 which is connected by a line terminating in a jack 103 may be connected b a switchin ofiice at which is locate a'cord circuit B terminating in plugs 101 and 102. From this ofiice the connection may be extended by the insertion of plug 101 into ack 104, and plug 102 into jack 200, throu h the contacts of relay 246 when operated, over the trunk circuit L, shown on Figs. 2 and 3.

The trunk circuit L terminates at the distant oflice in the plug 300 which maybe inserted into the ack 401 of a switching trunk C terminating in plug 402 at the office of the called subscribers station 400, which is connected to a line ending in jack 403. Relay 246 and 328 having been automatically operated as subsequently described, a conversational connection is now complete between the two subscribers.

The drawing of Fig. 2 shows a sending circuit S1. consisting of two thermionic tubes 205 and 206 arranged to transmit outward over the line L, various current combinations of different frequencies to cause the selective actuation of slow to release relays 301, 302 and 303 of receiving circuit R2 of Fig.3, initiating the performance of the necessary switching operations at the incoming/end of the trunk circuit to actuate the guard and disconnect signaling device 329, tosignal the called subscribers station 400, and to transmit back to the originating end of the trunk circuit predetermined signals to assist in the disestablishment of the connection. Similarly, slow to releaserelays 201, 202 and 203 are actuated, in response to a. similar sending circuit S2, to cause the performance of various switching operations at the outgoing end of the circuit necessary to actuate the supervisory signaling device 105 of cord circuit B, to

. transmit a busy back signal, and to cause the restoration to normal of apparatus used in establishing the connection. Relays 201, 202, 203, 301, 302 and 303 are made slow to release so that they will not release due to any momentary interruption of their normally closed circuits. On the drawings, these relays are shown with arrows intercepting their armatures and pointing in the direction in which the armature moves slowly. Relays 224, 225, 226, 324, 325 and 326 for controlling the above mentioned slow to release relays are of the polarized non-biased type, the armatures having no "normal positions but remaining in engagetrunk A with anment with either contact upon the cessadrawings. Assuming that the subscriber at the station 100 desires to communicate with the distant subscriber of station 400, the operator at the originating ofiice in response to the lighting of the lamp 107 extends the line of subscribers station 100, in the usual manner over call Wire trunk circuit A to the toll oflice at which is located cord circuit B. The operator having control of the cord circuit B, inserts plug 101 in jack 104, to ex tend the connection over the trunk circuit D in the manner hereinafter described. Communication is then established over a call wire circuit (not shown) with an incoming operator located at the end of trunk circuit L. This operator, upon being informed that a connection is desired with the line of subscriber 400, informs the operator at the out oing end that the connection may be ma e over the trunk L which may be one of a plurality of similar trunks extending between the twooflices. The outgoing operator inserts plug L into jack 200 and causes the operation of relay 207 over a circuit from grounded battery, through the winding of relay 106, sleeve contacts of plug 102 and jack 200, and the winding of relay 207 to ground. The operation of relay 207 causes the operation of relay 227 over a circuit from grounded battery, through the normal contact of relay 209, winding of marginal relay 227 and right-hand alternate contact of relay 207 to ground. The operation of relay 227 causes the operation of relay 210 current causes the tuning of the sending circuit S1 to be changed at the rate of approximately thirty-two times per second. Relay 211 is also operated over an obvious circuit which causes the sending circuit S1 to send out acombination of two current wave trains, each of a different frequency,

the frequency f the wave trains correspond-- The polarized relay 217 is also oping to the tuning resulting from the inclusion of the two condensers 212 and 214 in the sending circuit S1, the condenser 214 being connected to ound throu h the alternate contact of re ay 211 and to condenser 212 being connected intermittently to ground through the contacts of relay 245 and relay 217.

The outgoing current combination is transmitted through the windings of trans former 204 to which is connected an artificial line N1 of such impedance that there is no diiference of potential to outgoing current, across points 236 and'235 to which are connected the conductors leading to receiving circuit R1 which is, accordingly, not

' affected by the outgoing transmission of signaling current. T e. outgoing current traverses the conductors of line fto the distant ofiice, and enters the windings of the transformer 304 and passes to the receiving cir cuit R2 and into the primary winding of the transformer 318. Current is induced in the secondary winding and impresses a potential upon the grid circuit of the amplifying thermionic tube 319. An amplified cur rent is passed into the selectively tuned filter circuits 321 and 323. Currents are in duced in the secondary windings of transformers 331 and 333, and are passed into the grid circuits of the thermionic tubes 341 and 343, which results in the flow of a unidirectional current in the windings of polar ized non-biased relays 324 and 326. Both windings of relay 324 are energized, the armature of which relay is caused to vibrate back and forth at the rate of sixteen times per second in accordance with the frequency of the source of alternating current, 216. Although current also flows intermittently through the lower winding of the polarized non-biased relay 326, the armature of such relay will not vibrate. If the armature of this relay happens to be in engagement with its upper contact, the first impulse traversing the lower winding will move the armature into engagement with its lower contact and it will thereafter remain in this position until under some other condition, current is passed through the upper winding of the relay whereupon the armature will agaln reengage the upper contact.

;The interruption of the circuit of slow to release relay 303 while the armature moves from its upper to its lower contact is of insufiicient duration to permit that relay to release. The normally operated relay 301, under this condition does 1 not receive, through the vibrating contacts of relay 324,

' suflicient current to hold its armature in the normally operated condition, and accordingly releases and closes a circuit from battery through the winding of relay 327 and the contact of relay 301 to ground. Relay 327 is energized and closes a circuit from grounded battery through the normal contact of relay 328. right-hand alternate contact of relay 327 and lamp 329 to ground,

ment by themsertion of a cord circuit plug into jack 200 of the assigned line. Relay 327 in operating also closes a lockin circuit for itself extending from groundc battery through the winding of relay 327, its left-hand inner contact, and the right-hand normal contact of relay 334 to ground, bridging a circuit across the conductors of the trunk circuit including the retardation coil 335 and the winding of relay 336, through the outer left-hand contact of relay 327.

The incoming operator then inserts plug 300 into jack 401 of the switching trunk C. A circuit is then completed through the winding of relay 328 which may be traced from grounded battery through the winding of relay 328, sleeve contacts of plug 300 and jack 401 to ground. Relay 328 operates and closes the tip conductor of the line at its upper contacts, and extinguishes the lamp 329 by opening the circuit therethrough at its normal contact. A circuit is also completed through the winding of relay 336 which may be traced as follows: from grounded battery, right-hand winding of relay 404, outer normal contact of relay 405, lower left-hand winding of repeating coil 406, ring contacts of jack 401 and plug 300, outer contact of relay. 327, winding of relay 336, and of retardation coil 335, upper contact of relay 328, tip contacts of plug 300 and jack 401, upper left-hand winding of repeating coil 406, inner normal contact of relay 405, and to ground through the leithand winding of relay 404, which operates. Relay 336 is energized and operates relay 337 and slow-to-operate relay 333 over a circuit from grounded battery through the windings of relay 338 and relay 337 to ground through the contact of relay 336. The operation of these relays causes the operation of relay 339 through a circuit from grounded battery through the winding of relay 339, the alternate contact of relay 338, and the contact of relay 337 to ground. llelay 339, by its operation, causes the operation over an obvious circuit of relay 344, which connects grounded battery through its left-hand contact to junction point 315 of the sending circuit S2. which starts to oscillate. Relay 344 also closes a circuit from lays 311 and 345 over obvious circuits, which connect into the oscillator circuit; condensers 312 and 313 ca using alternate trains of current waves to be transmitted from the sending circuit into the primary winding of transformer 304. A balanced artificial line N2 of the proper impedance is connected across the windings of the transformer 304 so that no current from the sending circuit S2 is passed into the receiving circuit R2. The current from the sending c1rcuitS2 passes to the line L and enters the receiving circuit R1 at the distant station. Currents of a frequency corresponding to the inclusion in circuit of condensers 312 and 313 enter the filter circuits 221 and 222, and in a manner similar to that previously described in connection with the action of the receiving circuit R2, pass to the circuits of thetubes 241 and 242, and produce a unidirectional current to cause the operation of relay 225, and the release of relay 202. I

The release of relay 202 causes the operation of relay 229 over an obvious circuit, which connects resistance 208 in multiple with the winding of relay 207 reducing the resistance of the circuit of marginal relay 106 sufliciently to cause its operation and to light supervisory lamp 105 to notify the operator at the calling toll oflice that the connection is made to the trunk circuit G. The operation of relay 229 also causes the operation of relay 247 over an obvious circuit which in turn causes the operation of relay 228, which looks up through a circuit extending from grounded battery through the winding and left-hand contact of relay 228 and the left-hand alternate contact of relay 207 to ground. Relay 209 is also oper ated through the outside contact of relay 229 and locks up through a circuit from grounded battery through the winding and right-hand contact of relayf209, and the normal contact of relay 220. Due to the operation of relay 207, relays 210, 211 and 227 release. The reason for the operation of relays 209, 228 and 247 will appear from the subsequent description.

The operator at the originating toll oflice being advised "by the lowing of supervisory lamp 105 that the distant end of the trunk is connected to the trunk circuit C actuates the ringing key 108 which causes the operation of relay 234 over a circuit which may be: traced from source 110 of grounded ringing current, through the lower alternate contact of ringing key 108, ring contacts of plug 102 and jack 200, Winding of relay 234, condenser 250, retardation coil 251, tip contacts of jack 200 and plug 102 and the upper alternate contact of ringing key 108 to ground. Relay 234 causes, by its operation, the operation of relay 210 which starts the oscillator and causes the armature of relay 217 to vibrate in unison with the frequency of the alternating current supply 216. Under this condition condensers 212 and 213 are connected in the oscillator circuit which causes a frequency combination to be transmitted .over

the trunk circuit L which causes the oper- 346 which transmits current from ground and the source of rounded ringing current 347 through the a ternate contacts of relay 346, the upper contact of relay 328, the tip and ring conductors of the trunk L, tip and ring contacts of plug 300 and jack 401 throughthe windings of repeating coil 406, condenser 407 andthe winding of relay 408, which operates and causes the operation of relay 409 over an obvious circuit. Relay 409 by its operation impresses through its alternate contacts ringing current from the source 410 on the line of substation 400 through the tip and ring contacts of plug 402 and jack 403 which signals station 400 as long as the'operator in control of cord circuit B continues to hold the ringing key 108 actuated. When the receiver at station 400 is re -moved from its hook a circuit is closed from battery through the winding of relay 411, the conductors of trunk circuit C and the line and circuit of station 400. Relay 411 operates and closes a circuit which may be traced from battery, through the left-hand winding of rela 405, contact of relay 411, right-hand win ing of relay 405 to ground through the alternate contact of relay 404. Relay 405 operates and closes a circuit from. battery through the right-hand winding of relay ,404' toground at the outer alternate contact of relay 405 which maintains relay 404 operated.

Relay 405, by its operation, opens at itsv normal contacts the circuits previously traced for relay 336 which relay releases and in turn causes the release of relays 337, 338 and 339. The release of relay 339 causes the release of relay 344 which removes battery from the junction point 315 and stops the oscillation of the sending circuit S2. The circuit through relay 317 is also opened and relays 345 and 311 are released. The cessation of the current from the sending circuit S2 causes the operation of relay 202 of receiving circuit R1 which causes the release of relay 229 which disconnects the re sistance 208 shunting the winding of relay 207, which. increases the resistance of the sleeve circuit sufliciently to cause the release of cord circuit relay 106 extinguishing switchhook which causes the a receiver at station 100 is restored to the paratus of trunk circuit A to function in the well known manner causing the operation of supervisory relay 109; and thefjlighting of lamp 111. The replacing upon the hook of the receiver of station 400 causes the release of relay 411 and the opening of the circuit previously traced through the windings of relay 405 which releases. The release of this role again completes the circuit traced through relay 336 which operates and closes a circuit through relays 337 and 338. The operation of the latter causes the operation of relay 339 which again starts the oscillation of the sending circuit S2 and by the operation of relays 311 and 345 causes the transmission of the current combination which releases relay 202 of the receiving circuit R1, and the operation of relay 229 which reconnects the shunting resistance 208 which causes the operation of relay 106 and the operation of relay 247 which opens at its normal contact the operating circuit of relay 246 which releases and opens the circuit of the trunk line L.

The operator in control of cord circuit B noting the glowing of lamp 105 withdraws plug 102 from jaclr 200 causing the release of relays 106 and 207. Lamp 105 is extinguished and relay 228 releases, by the opening of the locking circuit at the lefthand contact of relay 207. The release of relay 207 closes a circuit which may be traced from grounded battery through its normal contact the winding of relay 227, left-hand alternate contact of relay 209 and through the winding of relay 239 to ground. Relay 227 is marginal and does not operate in series with relay 239 which relay, however, operates and starts the oscillation of the sending circuit S1, as previously described, and operates relays 211 and 245 which connect condensers 213 and 214 in circuit and cause the transmission of currents which release relay 302 of the receiving circuit R2. The release of the latter relay operates relay 334 which opens the locking circuit of relay 327 which releases and closes a circuit which may be traced from grounded battery through the lower alternate contact of relay 328 and the righthand normal contact of relay 327 to ground through the lamp 329, which is lighted as a disconnect signal. The operation of relay 334 also causes, as previously described, transmission of current which releases relay 203 of, the receiving circuit R1 and operates over an obvious circuit relay 220 which releases relays 209 and 239. The release of the latter relay releases relays 211 and 245 and discontinues the operation of sending circuit S1. When the corresponding currents from circuit- Sl no longer are received at the incoming end of the trunk circuit, relay 302 inserted into jack 412, the

operates and relay 334 releases and sending circuit S2 ceases to function which causes the operation of the normally operated relay 203 and the release of relay 220.

If the operator in charge of the incoming end of trunk circuit C finds the line of Sn scribers station 400 busy, plug 402 is then t1p and ring contacts of which are in series with an mterrupter 413which causes rela 411 to operate and release in unison with the frequency of the interruptions. This causes relay 405 to operate similarly by reason of the circuit through its winding and the contact of relay 411 previously traced. As a result of this circuit relay 336 operates and releases intermittently, which in turn operates and releases relay 337, but not the slow to operate relay 338. This causes the operation of relay 340, which in turn starts the sendin circuit S2, and operates relay 345, whic leaves condensers 312 and 314 connected in the sending circuit. The frequency of the currents corresponding to this connection causes the release of relay 201 which connects the shunting resistance 208 to an intermittent ground through an interrupter 248. As a result, relay 106 is intermittently operated causin the flashing of lamp 105 in dicative to t e operator that the line of station 400 is busy.

When the operator in control of the incoming end of trunk circuit L in response to the glowing of the disconnect lamp 329 withdraws the plug 300 from jack 401, relay 328 releases, extinguishing the lamp 329, and all apparatus is now restored to normal.

7 What is claimed is:

1. A telephone exchange system comprising two telephone central ofices, a trunlr 5 line interconnecting said ofiices, means for producing a plurality of currents each oi a dii'ierent frequency associated with each central oiiice, a receiving circuit associated with each central oilice, signaling devices asso 1m ciated with said receiving circuit, said receiving circuit being difierently responsive to various combinations of said currents from the other central oihce to actuate correspondingly said signaling devices.

2. A telephone exchange system comprising two telephone central offices, a subscribers station associated with each central office, a trunk circuit connecting the two offices, means for producing a plurality of 120 currents each of a difierent frequency associated with each office, and means for transmitting and receiving various combinations of currentstover said trunk circuit to signal the station of the called subscriber and to 125 supervise the connection thereto.

3. The method of signaling a called subscribers station and of supervising the connection thereto over a transmission medium extending between two distant central tele- 130 phone ofiices by the transmission and the selective receiving of predetermined combinations of current impulses of different frequencies.

4. telephone exchange system comprising two telephone central offices, a transmis- ,sion medium between said offices, means for producing a plurality of currents at each oflice each of a different frequency, means for transmitting over said medlum various predetermined combinations of said currents, supervisory signaling devices at each 'office,

signaling devices at each office, a trunk-line interconnectin said offices, means for producing a plura ity of currents each of a different frequency associated with each central oflice, means for transmitting'predetermined combinations of said currents over said trunk line, a'receiving circuit ateach office having sections each tuned to respond to the frequency of each component of the predetermined current combinations, and means responsive to the oint response of the tuned sections to actuate sa1d supervisor;

and a receiving circuit at each oflice responsigznaling devices.

sive selectively and differently to varlous predetermined current combinations to cause the operation of said signaling devices.

5. A telephone exchange system comprising two telephone central ofiices, a called subscribers station associated with one office, a calling subscrlbers station associated. wlth the other office, a tIBJlSIIllSSlOIl l1ne between said oflices for interconnecting said calland control the connection, and means at the oflice associated with the calling subscribers station for sending a predetermined combination of said currents over said transmission line to the receiving circuit at the distant office to restore said electromagnetic switching devices thereat to normal, and to cause a predetermined current combination to be sent to the receiving circuit at' the firstmentioned office to cause the restoration to normal of said electromagnetic switching devices at the first oflice.

6. A telephone exchange system comprising two telephone central ofiices, supervisory A telephone exchange system comprising two telephone central offices, a calling subscribers station associated with one oflice, a called subscribers station associated with the other oflice, a trunk circuit interconnecting said offices, means at each oflice for interconnecting the associated subscribers station with said trunk, supervisory signaling devices associatedwith said interconnecting means at the ofiice associated with the call ing subscribers station and with the trunk circuit at the oflice associated with the called subscribers station, means for producing a plurality of currents of different frequencies, receiving circuits at each office each responding differently to actuate said supervisory signaling devices, in correspondence withvarious predetermined combinations of said currents originating at the other office and received over said trunk circuit.

8. A signaling system comprising a transmission circuit, avacuum tube oscillator adapted to produce a plurality of current frequencies, means for controlling-said oscillator to select any one of a plurality of groups of frequencies and to sequentially impress frequencies of a selected group on said circuit. In witness whereof, I hereunto subscribe my name this 1st day of April, A. D. 1921.

PAUL B. 'MURPHY. 

